25. An examination of the effect of ‘wake chopping’ on droplet sizes in steam turbines

Bakhtar, F.; Heaton, Alan

doi:10.1680/totpowws.13957.0028

Cited by 8 publications

(3 citation statements)

References 7 publications

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“…The method accounts for the effect of wake chopping on droplet sizes. 22,23 It is based on the random character of dissipation experienced by fluid particles passing through the multistage turbine, depending on a randomly chosen streamline (2D approach) within each blade row with a given pitchwise distribution of polytropic efficiency. Different fluid particles thus undergo different nucleation conditions resulting in a broader droplet size distribution.…”

Section: Wet Steam Energy Lossmentioning

confidence: 99%

The assessment of the effect of binary homogeneous nucleation on wet steam energy loss in a low pressure steam turbine

Petr

Kolovratník

2014

Proceedings of the Institution of Mechanical Engineers, Part A:

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The objective of the paper was to recognize the possible effect of a low concentration of chemical impurity (NaCl) present in the inlet steam (2.27 ppb) in the assessment of the wet steam energy loss occurring in a 1000 MW nuclear low pressure steam turbine. The presented analysis suggests that the used binary nucleation model, accounting for the electrolytic nature of the droplets, predicts a reduced wet steam energy loss of order -9 %, in comparison with the unary pure steam droplet nucleation model. This minor difference, considering the uncertainties of the existing measurements and the incomplete knowledge of the real droplet nucleation conditions in the steam of the turbine (primarily in relation to the necessary input data of chemical impurities), suggests that unary pure steam droplet nucleation (Becker-Dö ring) is an acceptable approximation at the current state of knowledge.

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Section: Wet Steam Energy Lossmentioning

confidence: 99%

The assessment of the effect of binary homogeneous nucleation on wet steam energy loss in a low pressure steam turbine

Petr

Kolovratník

2014

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…This source initiates highfrequency pressure and temperature fluctuations that interfere with the nucleation process in the entire cross-section from blade to blade and trigger the time-dependent droplet size distribution behind the cascade. The related unsteady phenomenon is known as wake chopping (see, for instance, the investigation of Bakhtar and Heaton [53]). Figure 45 shows numerical results of the turbulent flow simulation through a VKI 1 rotor, the steam is assumed to condense homogeneously, heterogeneous effects are excluded.…”

Section: Wake Interactionsmentioning

confidence: 99%

Unsteadiness in Condensing Flow: Dynamics of Internal Flows with Phase Transition and Application to Turbomachinery

Schnerr

2005

Proceedings of the Institution of Mechanical Engineers, Part C:

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Steady flows of condensable fluids may become unsteady if one component of the fluid starts to condense. In high-speed expansion flows, typical for large-scale steam turbines, the subcooled vapour state collapses after nucleation, typically in flow regimes close to Mach number 1. After the formation of steady shocks, instantaneous thermal choking initiates selfexcited high-frequency oscillations which is the focus of this article. The driving mechanism is the interaction of compressibility and energy supply in flows close to maximum mass flux density and is therefore not controlled by the viscosity of the fluid. Additional viscosity-driven excitation mechanisms exist and superpose the primary diabatic instability, especially in axial cascades. Typical are shedded shear layers from blade trailing edges and the periodic interference of wakes separating from the stator with the rotor blades. This article presents a review of the authors and various co-workers' research, supplemented by important references to complete the subject under consideration. This article starts with an introduction in the most simple flow model of given heat addition in constant area flow and ends with mixed homogeneous/heterogeneous condensation in a transonic axial cascade stage with a high-resolution sliding interface for preservation of submicron condensate convected from the stator into the rotor. Numerical simulations are compared with experiments of flows with and without carrier gas.

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“…The foundations of wake chopping models were presented by Gyarmathy & Spengler (1974), and provide a methodology for the analysis of the steam temperature fluctuations observed by Wood (1973). Their ideas were subsequently implemented as a proof of concept by Bakhtar & Heaton (1989) and further developed with a more theoretical basis by Guha & Young (1994). The stochastic modelling approach to wake chopping is based on an efficiency distribution across the pitch and the random pitchwise inlet location of fluid parcels at the leading edge of blade rows, thus effectively defining a set of random thermodynamic histories through the machine.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Wake Chopping on Wet-Steam Turbine Modelling

Vasilj¹,

Schuster²,

White³

2021

Preprint

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25. An examination of the effect of ‘wake chopping’ on droplet sizes in steam turbines

Cited by 8 publications

References 7 publications

The assessment of the effect of binary homogeneous nucleation on wet steam energy loss in a low pressure steam turbine

The assessment of the effect of binary homogeneous nucleation on wet steam energy loss in a low pressure steam turbine

Unsteadiness in Condensing Flow: Dynamics of Internal Flows with Phase Transition and Application to Turbomachinery

The Influence of Wake Chopping on Wet-Steam Turbine Modelling

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